The choice of ridge tile is the height of importance on any roofing project. Ged Ferris, Marketing Manager at Cembrit, explains why.
In the vast majority of cases, the top of a pitched slate or tiled roof (i.e. the ridge) is usually fitted with ridge tiles which sit astride the apex and overlap onto the roof covering on both sides.
This bridging function, which effectively seals both sides of the roof together, makes it important, for a number of reasons, to specify and fit the the right ridge tiles for your roof. Most obviously, the ridge tiles seal the apex of the roof from the environment, and prevent ingress of water.
Increasingly though, the choice of ridge tile can play a role in effective ventilation of a roof – this is especially so in the case when fibre cement slates are used at the roof covering.
Ensuring that a roof space is properly ventilated is an essential step when replacing or refurbishing a roof.
Proper ventilation is vital in order to prevent the build up of condensation and related problems which result when a roof space is unable to ‘breathe’. On most houses this means from eaves to eaves, but supplementing this with ridge ventilation will help with any “stale” air pockets.
Fibre cement slates are ‘tight fitting’ i.e. smooth and uniform and often, a roof finished in this material lack the passive ventilation achieved by more uneven materials.
This means when using FC slates, on an insulated roof slope, the batten void will require ventilation. This point is very well covered by the BS 5250: 2002, but it is worth reinforcing that with a tight fitting or interlocking roof system, such as fibre cement slate, there will be a need to have additional ventilation between the batten void.
A properly chosen ridge tile for the project, specifically designed for ventilation, has an important role to play in meeting the standard, as it creates the greatest area of outlet for warm moisture bearing air.
A correctly chosen type of ridge tile will also complete the look of your roof. It is common practice to use wet fixed concrete ridge tiles on a fibre cement roofs.
The latest versions of BS 5534 and BS 8000-6 do not recommend this, as adhesion between the mortar and non-porous coating on the slate is difficult, furthermore is the problem of the correct mortar mix for fixing, as well as the perennial challenge for builders in the UK – waiting for dry weather before fitting the ridges. All ridges now need to be mechanally fixed.
Although this is well established amongst builders, concrete has its drawbacks. Aesthetically, a concrete ridge tile is not a good fit with a fibre cement slate roof. An FC roof is known and widely admired for its sleek uniform finish. A bulky, concrete ridge tile can spoil this look. Concrete ridge tiles are also heavy, which can present problems for contrators on installation.
There is an alternative to using concrete ridge tiles, and that is to use fibre cement. There are many benefits in using fibre cement ridges – FC ridges fit the smooth, flush look of FC slates – they are also lighter in weight than concrete alternatives, making them easier to install.
Not only that, FC ridges don’t require electric power for cutting, or any dust suppression equipment. Moreover, FC ridges are dry fixed with readily available “sela” type screws and installation is not dependent on getting the correct mortar mix, nor having to wait for dry weather.
We have developed a continuously ventilated FC ridge tile, which is both designed to cope with typical roof pitches, as well as helping the roof design comply with the latest version of BS 5250. As such, it is an ideal solution for tricky ventilation problems, such as where there is no clear airpath from eaves to ridge.
We also have supplementary low-profile vents available for use on the roof slope. They are unobtrusive and can also be used as terminals.
Manufactured from the same raw materials and pigments as our fibre cement slate the ridges are the perfect complement to a Cembrit fibre cement roof. The products match the slate colour, with no unsightly protrusions or changes of angle, contributing to the sleek effect that can be achieved with our BBA-certified fibre cement slates.
Increasing demands for energy efficiency through improved levels of insulation, means ventilation at roof level is more crucial. The most efficient solution will incorporate inlets at the eaves with outlets along the length of the apex. Following this advice will also ensure the roof complies with the latest editions of BS 5534, BS 8000-6 and chapter 7.2 of the NHBC recommendations.